Use of divalent metal salt image amplifiers in photosensitive and thermosensitive elements

ABSTRACT

A divalent metal salt, such as zinc acetate, cadmium acetate or cupric acetate, in combination with an oxidation-reduction imageforming combination containing a heavy metal salt oxidizing agent, such as silver behenate, and a reducing agent, such as a bis-naphthol reducing agent, in a photosensitive and thermosensitive element suitable for dry processing with heat, provides increased image density with no adverse increase in background density. A combination of a bis- Beta -naphthol reducing agent and zinc acetate, cadmium acetate or cupric acetate in conjunction with a stable source of silver for physical development is useful in photosensitive elements for dry processing with heat. The element can contain a sensitizing dye, an activator-toning agent and other addenda employed in elements for dry processing with heat. A stable, developed image can be provided by heating the element after exposure. The photosensitive component can be photographic silver halide or other suitable photosensitive metal salts.

United States Patent 91 Hillel 1 Jan. 2, 1973 [54] USE OF DIVALENT METALSALT IMAGE AMPLIFIERS IN PHOTOSENSITIVE AND THERMOSENSITIVE ELEMENTS[75] Inventor: Gary Lynn Hiller, Rochester, NY.

[73] Assignee: Eastman Kodak Co., Rochester,

[22] Filed: June3, 1970 [21] Appl. No.: 43,173

Puerckhauer Ohkubo ..96/1 14.1

FOREIGN PATENTS OR APPLICATIONS 1,161,777 9/1969 Great Britain OTHERPUBLICATIONS Chemical Abstracts, Vol. 68, 1968, pg. 64585,

reference at 64592f, Light-developable printing-out photosensitivematerial.

Primary Examiner-J. Travis Brown Assistant Examiner-Judson R. HightowerAttorney-W. H. J. Kline, Bernard D. Wiese and Richard E. Knapp ABSTRACTA divalent metal salt, such as zinc acetate, cadmium acetate or cupricacetate, in combination with an oxidation-reduction image-formingcombination containing a heavy metal salt oxidizing agent, such assilver behenate, and a reducing agent, such as a bis-naphthol reducingagent, in a photosensitive and thermosensitive element suitable for dryprocessing with heat, provides increased image density with no adverseincrease in background density. A combination of a bis-B- naphtholreducing agent and zinc acetate, cadmium acetate or cupric acetate inconjunction with a stable source of silver for physical development isuseful in photosensitive elements for dry processing with heat. Theelement can contain a sensitizing dye, an activator-toning agent andother addenda employed in elements for dry processing with heat. Astable, developed image can be provided by heating the element afterexposure. The photosensitive component can be photographic silver halideor other suitable photosensitive metal salts.

27 Claims, No Drawings USE OF DIVALENT METAL SALT IMAGE AMPLIFIERS INPHOTOSENSITIVE AND TI-IERMOSENSITIVE ELEMENTS BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates tophotosensitive elements, compositions and processes for developing alatent image using so-called dry processing with heat. In one lates to adry process of developing and increasing the maximum image density in aphotosensitive and thermosensitive element containing a reducing agent,an oxidizing agent and an image-amplifying divalent metal salt, asdescribed 2. Description of the State of the Art It is known that, in aphotographic element containing a gelatin-peptized silver halideemulsion, watersoluble inorganic acid salts can be used to inhibit fogin both fresh and incubated coatings. They are particularly effective inphotographic elements sensitized by alkylene oxide polymers, asdescribed in U.S. Pat. No. 2,839,405 ofJones published June 17,1958.

Metallic salts, such as stannous stearate, are known image amplifiersfor a thermographic, non-silver halide image-receptor sheet, such asdescribed in U.S. Pat. No. 3,460,946 of Puerckhaver et al. issued Aug.12, 1969. These image-receptor sheets contain a reducing agent, such as2,6-ditertiary -butyl-pcresol, an oxidizing agent such as silverbehenate and a toner, e.g., (2H )-phthalazinone; however, they are notphotosensitive. An intermediate photosensitive sheet containing, forexample, 4-methoxy-l-naphthol is first given a reflex exposure while incontact with the original. The exposed photosensitive intermediate sheetis then heated while in contact with the image-receptor sheet.

It is known to obtain an image in a photosensitive element suitable forso-called dry processing with heat. The photosensitive element cancontain a reducing agent, a light insensitive silver salt of an organicacid as an oxidizing agent and photographic silver halide, such asdescribed in U.S. Pat. No. 3,152,904 of Sorensen and Shepard issued Oct.13, 1964, and U.S. Pat. No. 3,457,075 of Morgan and Shely issued July22, 1969. Elements of this type are also described, for example, inFrench Pat. No. 1,441,619 and Belgian Pat. No. 705,872.

It is also known that the addition of mercuric ion, e.g., in the form ofmercuric acetate at about 0.005 to about 0.05 mole per mole of silver,to a heat-developable photographic printing sheet containingphotographic silver halide, an organic silver salt and a reducin g agentcauses an increase in photographic speed and acts as an image amplifier,as well as an incubation antifoggant, as described in German Pat. No.1,908,761

issued Feb. 18, 1969, or corresponding South African Pat. No. 903,080published Feb. 27, 1969.

Unfortunately, in some cases these elements suffer from having poorspectral sensitivity and in some cases the resulting images afterprocessing are of low maximum density, undesirably warm tone and havehigh background density.

There has been a continuing need for a photosensitive andthermosensitive element which provides higher image density, a moreneutral (black) tone and less background density due to poorpost-processing print-out.

SUMMARY OF THE INVENTION According to the invention, the describedimprovements are provided in a photosensitive and thermosensitiveelement composition or process with an oxidation-reduction image-formingcombination comprising (i) a heavy metal salt oxidizing agent with (ii)a reducing agent, a catalyst for said oxidation-reduction imageformingcombination and a binder, by employing a divalent metal salt imageamplifier, which is a zinc, cadmium or copper salt, with the describedcombination.

DETAILED DESCRIPTION OF THE INVENTION A number of divalent metal saltswhich are image amplifiers can be employed in the practice of theinvention to cause an increase in maximum image density with moreneutral'tone without undesirably increased background density. Asuitable image-amplifying compound is a divalent metal salt, e.g., azinc salt such as zinc acetate. Other suitable inorganic divalent metalsalts which can be employed in the practice of the invention includeacetate salts of cadmium and copper.

The described image-amplifying compounds are suitable in a range ofconcentration of about 0.005 to about 0.20 mole of divalent metal saltper mole of heavy metal salt oxidizing agent, e.g., per mole of silversalt oxidizing agent; however, they are especially suitable at aconcentration of about 0.010 mole to about 0.10 mole of divalent metalsalt per mole of silver salt oxidizing agent.

hotosensitive and thermosensitive elements, which are suitable for dryprocessing with heat, can provide a developed image by physicaldevelopment as described, for example, in U.S. Pat. No. 3,457,075 ofMorgan et al. issued July 22, 1969. Other elements of this type aredescribed, for example, in U.S. Pat. No. 3,429,706 of Shepard et al.issued Feb. 25, 1969, and U.S. Pat. No. 3,152,904 of Sorensen et a1.issued Oct. 13, 1964. V

The described element contains a photosensitive salt, especially aphotosensitive silver salt. It is believed this is a catalyst for thedescribed oxidation-reduction image-forming combination. A typicalconcentration range of photosensitive silver salt is about 0.005 toabout 0.50 mole of photosensitive silver salt per mole of heavy metalsalt oxidizing agent, e.g., per mole of silver behenate. Preferredphotosensitive silver salts are photosensitive silver halides, e.g.,silver chloride, silver bromide, silver bromoiodide, chlorobromoiodide,or mixtures thereof. The photosensitive silver halide can be coarseorfinegrain, very fine-grain emulsions being especially useful. Theemulsion containing the photosensitive silver hasilver.

lide can be prepared by any of the well-known procedures in thephotographic art, such as single-jet emulsions, double-jet emulsions,such as Lippmann emulsions. ammoniacal emulsions, thiocyanate orthioether ripened emulsions, such as those described in U.S. Pat. No.2,222,264 of Nietz et al. issued Nov. 14, 1940, U.S. Pat. No. 3,320,069of lllingsworth issued May 15,1967, and U.S. Pat. No. 3,271,157 ofMcBride issued Sept. 6, 1966. Surface-image silver halide emulsions canbe used. If desired, mixtures of surfaceand internal-image silver halideemulsions can be used as described in U.S. Pat. No. 2,996,332 of Luckeyet al. is-

.sued Apr. 15, 1961. Negative-type emulsions can be used. The silverhalide emulsion can be a regular-grain emulsion such as described inKlein and Moisar, Journal ofPhotographic Science, Volume 12, No. 5,Sept.- Oct. 1964), pages 24225 1.

The silver halide emulsions employed in the practice of the inventioncan be unwashed or washed to remove soluble salts. In the latter case,the soluble salts can be removed by chill setting and leaching or theemulsion can be coagulation washed.

The silver halide employed in the practice of the invention can besensitized with chemical sensitizers, such as with reducing agents;sulfur, selenium or tellurium compounds; gold, platinum or palladiumcompounds; or combinations of these. Suitable procedures are described,for example, in U.S. Pat. No. 1,623,499 of Shepard issued Apr. 5, 1927;U.S. Pat. No. 2,399,083 of Waller et al. issued Apr. 23, 1946; U.S. Pat.No. 3,297,447 of McVeigh issued Jan. 10, 1967; and U.S. Pat. No.3,297,446 of Dunn issued Jan. 10, 1967.

Photosensitive silver halide emulsions employed in the practice of theinvention can be protected against the production of fog and can bestabilized against loss of sensitivity during keeping. Suitableantifoggants and stabilizers, e.g., used alone or in combination,include, for example, thiazolium salts; azaindenes; mercury salts asdescribed, for example, in U.S. Pat. No. 2,728,663 of Allen et al.issued Dec. 27, 1955; urazoles; sulfocatechols; oximes described, forexample, in British Pat. No. 623,448; nitron; nitroindazoles; polyvalentmetal salts described, for example, in U.S. Pat. No. 2,839,405 of Jonesissued June 17, 1958; platinum, palladium and gold salts described, forexample, in U.S. Pat. No. 2,566,263 of Trivelli et al. issued Aug. 28,1951, and U.S. Pat. No. 2,597,915 of Yutzy et al. issued May 27,1952. 1

Suitable organic reducing agents which can be employed in the describedcombination include, for example, phenol and naphthol reducing agents.The bisnaphthol which is preferred is a bis-B-naphthol of the formula:

wherein R, and/or R are hydrogen, alkyl with one to three carbon atoms,alkoxy, e.g., alkoxy containing one to two carbon atoms, such as methoxyor ethoxy; halogen, nitro, amino or a diazonium halide salt, and n is 0or 1. Suitable bis-B-naphthols which can be employed in the practice ofthe invention include:

2,2'-dihydro xy- 1 ,1 -binaphthyl,6,6'-dibromo-2,2'-dihydroxy-1,1'-binaphthyl,6,6'-dinitro-2,2-dihydroxy-1,1'-binaphthyl and/orbis-(2-hydroxy-l-naphthyl)methane. The described reducing agents aresuitable in a range of concentration; however, they are especiallysuitable at a concentration from about 0.10 to about 2.0 moles, e.g.,about 0.40 mole to about 0.75 mole, of reducing agent per mole ofoxidizing agent, as described.

Other reducing agents, which are typically silver halide developingagents, can be used in conjunction with the above bis-naphthol reducingagents. Suitable silver halide developing agents include, for example,polyhydroxybenzenes such as hydroquinone developing agents, e.g.,hydroquinone, alkyl-substituted hydroquinones as exemplified by tertiarybutylhydroquinone, methylhydroquinone, 2,5-dimethylhydroquinone and2,6-dimethylhydroquinone; catechols and pyrogallol; halo-substitutedhydroquinones such as chlorohydroquinone or dichlorohydroquinone;alkoxy-substituted hydroquinones such as methoxyhydroquinone orethoxyhydroquinone; methylhydroxynaphthalene; phenylenediaminedeveloping agents; methylgallate; aminophenol developing agents, such as2,4- diaminophenols and methylaminophenols; ascorbic acid developingagents such as ascorbic acid, ascorbic acid ketals and ascorbic acidderivatives such as those described in U.S. Pat. No. 3,337,342 of Greenissued Aug. 22, 1967; hydroxylamine developing agents such asN,N'-di-(2-ethoxyethyl)hydroxylamine; 3- pyrazolidone developing agentssuch as l-plienyl-3- pyrazolidone and 4-methyl-4-hydroxymethyl-l-phenyl-3-pyrazolidone'including those described in British Pat. No. 930,572published July 3, 1963; hydroxytetronic acid, and hydroxytetronimidedeveloping agents, reductone developing agents such asanhydrodihydropyrrolidino hexose reductone; and.the like.

It is desirable to employ an activator-toning agent in the elements,compositions and processes of the invention to obtain a desired image,particularly 'when phenolic reducing agents are used. A suitableactivatortoning agent is a heterocyclic activator-toning agentcontaining at least one nitrogen atom and of the formula:

where R is hydrogen, hydroxyl, or a metal ion such as potassium, sodium,lithium, silver, gold or mercury; Z represents atoms completing aheterocyclic nucleus, especially a 5- or 6-member heterocyclic nucleus.The atoms completing the heterocyclic nucleus can be, for example,

or an alkylene group containing three or four carbon 5 moiety, in aphotosensitive and thermosensitive eleatoms. The atoms completing theheterocyclic nucleus can contain various substituent groups, such asamino, alkyl amino, e.g., methylamino or ethylamino, hydroxyl, carbamyland the like. An especially suitable activator-toning agent is aheterocyclic activatortoning agent containing at least one nitrogen atomwhich is preferably a cyclicimide of the formula:

wherein R can be hydrogen, hydroxyl, or a metal ion such as potassium,sodium, lithium, silver, gold or mercury; Z represents carbon atoms of aseries completing a cyclicimide nucleus, typically consisting of fromfive to six carbon atoms, e.g., a phthalimide or succinimide nucleus.The atoms of the cyclicimide nucleus can contain various substituentgroups, especially amino, alkyl, such as alkyl containing one to fivecarbon atoms, such as methyl, ethyl, propyl, butyl or pentyl or aryl,such as aryl containing six to 20 carbon atoms, such as phenyl, tolyland xylyl.

Examples of suitable activator-toning agents which can be employed inthe practice of the invention include:

phthalimide,

N-hydroxyphthalimide,

N-potassium phthalimide,

N-silver phthalimide,

N-mercury phthalimide,

succinimide and/or N-hydroxysuccinimide.

The described activator-toning agents are suitable in a range ofconcentration depending on several factors such as the desired image,the particular oxidationre'duction image-forming combination, processingtem-' perature and the like. However, they are especially suitable at aconcentration from about 0.10 mole to about 1.05 moles ofactivator-toning agent per mole of oxidizing agent, as described.

Other so-called activator-toning agents can be employed in combinationwith other components of the described photosensitive andthermosensitive element in the practice of the invention. Variouscompounds which have been designated as toners can be employed for thispurpose. Typically, a heterocyclic organic toning agent containing atleast two hetero atoms in the heterocyclic ring of which at least one isa nitrogen atom is employed. These are described, for example, in U.S.Pat. No. 3,080,254 of Grant issued Mar. 5, 1963. Suitable tonersinclude, for example, phthalazinone, phthalic anhydride,2-acetylphthalazinone and 2- phthalylphthalazinone. Other suitabletoners are described, for example, in U.S. Pat. No. 3,446,648 of Workmanissued May 27, 1969.

A non-aqueous, polar, organic solvent, such as a compound containing ament suitable for dry processing with heat can provide improved maximumimage densities, e.g., tetrahydrothiophene-1,1-dioxide,4-hydroxybutanoic acid lactone and/or methylsulfinylmethane.

The described elements comprise a heavy metal salt oxidizing agent,especially a silver salt oxidizing agent, e.g., a silver salt of anorganic acid. The silver salt of the organic acid should be resistant todarkening under illumination to prevent undesired deterioration of adeveloped image. An especially suitable class of silver salts of organicacids is represented by the water-soluble silver salts of organic acidsof long-chain fatty acids which are stable to light. Compounds which aresuitable silver salts include, for example, silver behenate, silverstearate, silver oleate, silver laurate, silver hydroxystearate, silvercaprate, silver myristate and silver palmitate. Other suitable oxidizingagents are, for example, silver benzoate, silver phthalazinone, silverbenzotriazole, silver saccharin, silver4'-n-octadecyloxydiphenyl-4-carboxylic acid, silver O-aminobenzoate,silver acetamidobenzoate, silver furoate, silver camphorate, silverP-phenylbenzoate, silver phenylacetate, silver salicylate, silverbutyrate, silver terephthalate, silver phthalate, silver acetate andsilver acid phthalate. Oxidizing agents which are not silver salts canbe employed, if desired, such as zinc oxide, gold stearate, mercuricbehenate, auric behenate and the like, but silver salts are preferred.

A photosensitive and thermosensitive element, and emulsions describedand used in the practice of the invention, can contain various colloidsalone or in combination as vehicles, binding agents and in variouslayers. Suitable materials are typically hydrophobic, but hydrophilicmaterials can also be employed. They are transparent or translucent andinclude both naturally occurring substances such as proteins, forexample, gelatin, gelatin derivatives, cellulose derivatives,polysaccharides such as dextran, gum arabic and the like; and syntheticpolymeric substances such as watersoluble polyvinyl compounds likepoly(vinyl pyrrolidone), acrylamide polymers and the like. Othersynthetic polymeric compounds which can be employed include dispersedvinyl compounds such as in latex form and particularly those whichincrease dimensional stability of photographic materials. Suitablesynthetic polymers include those described in U.S. Pat. No. 3,142,586 ofNottorf issued July 28, 1964; U.S. Pat. No. 3,193,386 of White issuedJuly 6, 1955; U.S. Pat. No. 3,062,674 of Houck et al. issued Nov. 6,1962; U.S. Pat. No. 3,220,844 of l-louck et al. issued Nov. 30, 1965;U.S. Pat. No. 3,287,289 of Ream et al. issued Nov. 22, 1966; and US.Pat. No. 3,411,911 of Dykstra issued Nov. 19, 1968. Effective polymersinclude water-insoluble polymers of alkyl acrylates and methacrylates,acrylic acid, sulfoalkyl acrylates or methacrylates, and those whichhave cross-linking sites which facilitate hardening or curing, as wellas those having recurring sulfobetaine units as described in CanadianPat. No. 774,054. Preferred high-molecularweight materials and resinsinclude polyvinyl butyral, cellulose acetate butyrate, polymethylmethacrylate,

poly(vinylacetal) film, polystyrene film, poly(ethylene terephthalate)film, polycarbonate film and related films or resinous materials, aswell as glass, paper, metal and the like. Typically, a flexible supportis employed, especially a paper support which can bepartially-acetylated or coated with baryta and/or an alphaolefinpolymer, particularly a polymer of an alphaolefin containing two to 10-carbon atoms such as polyethylene, polypropylene, ethylene-butenecopolymers and the like.

The photosensitive and thermosensitive and other hardenable layers of anelement used in the practice of this invention can be hardened byvarious organic or inorganic hardeners, alone or in combination, such asaldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acidderivatives, sulfonate esters, sulfonyl halides and vinyl sulfonylethers, active halogen compounds, epoxy compounds, aziridines, activeolefins, isocyanates, carbodiimides, mixed-function hardeners andpolymeric hardeners such as oxidized polysaccharides like dialdehydestarch and oxyguargum and the like.

The photosensitive and thermosensitive elements used in the practice ofthe invention can contain antistatic or conducting layers. Such layerscan comprise soluble salts such as chlorides, nitrates and the like,evaporated metal layers, ionic polymers such as those described in U.S.Pat. No. 2,861,056 of Minsk issued Nov. 18, 1958, and U.S. Pat. No.3,206,312 of Sterman et al. issued Sept. 14,1965, or insoluble inorganicsalts such as those described in U.S. Pat. No. 3,438,451 of Trevoyissued Feb. 18, 1969. The photosensitive and thermosensitive elementscan also contain antihalation materials and antihalation dyes.

The photosensitive and thermosensitive layers or other layers employedin the practice of the invention can contain plasticizers andlubricants. Suitable plasticizers and lubricants include, for example,polyalcohols such as glycerin and diols described, for example, in U.S.Pat. No. 2,960,404 of Milton -et al. issued Nov. 1, 1966; fatty acids oresters such as those described in U.S. Pat. No. 2,558,765 of Robijnsissued Mar. 11, 1952; U.S. Pat. No. 3,l2l,060 of Duane issued Feb. 11,1964; and silicone resins such as those described in British Pat. No.955,061.

The photosensitive and thermosensitive layers or other layers employedin the practice of the invention can contain surfactants such assaponin; anionic compounds such as alkyl aryl sulfonates described, forexample, in U.S. Pat. No. 2,600,831 of Baldsiefen issued June 17, 1962;amphoteric compounds such as those described in U.S. Pat. No. 3,133,816of Ben-Ezra issued May 19, 1964; and adducts of glycidol and an alkylphenol such as those described in British Pat. No. 1,022,878.

If desired, the photosensitive and thermosensitive elements employed inthe practice of the invention can contain matting agents such as starch,titanium dioxide, zinc oxide, silica, polymeric beads including beadsdescribed, for example, in U.S. Pat. No. 2,922,101 of Jelley et, al.issued July 11, 1961, and us. Pat. No. 2,701,245 of Lynn issued Feb. 1,1955.

The photosensitive and thermosensitive elements employed in the practiceof the invention can contain brightening agents including stilbenes,triazines, oxazoles and coumarin brightening agents. Water-solublebrightening agents can be used such as those described in German PatentNo. 972,067 and U.S. Pat. No. 2,933,390 of McFall et al. issued April19, 1960, or dispersions of brighteners can be used such as thosedescribed in German Pat. No. 1,150,274, U.S. Pat. No. 3,406,070 ofOetiker et al. issued Oct. 15, 1968, and French Pat. No. 1,530,244.

The various layers including the photosensitive and thermosensitivelayers of an element employed in the practice of the invention cancontain light-absorbing materials, filter dyes, antihalation dyes andabsorbing dyes such as those described in U.S. Pat. No. 3,253,921 ofSawdey issued May 31, 1966; U.S. Pat. No. 2,274,782 ofGaspar issued Mar.3, 1942; U.S. Pat. No. 2,527,583 of Silberstein et al. issued Oct. 311950; and U.S. Pat. No. 2,956,879 of VanCampen issued Oct. 18, 1960. Ifdesired, the dyes can be mordanted, for example, asdescribed in U.S.Pat. No. 3,282,699 of Jones et al. issued Nov. 1, 1966.

The photosensitive and thermosensitive layers used in the practice ofthe invention can be coated by various coating procedures including dipcoating, airknife coating, curtain coating or extrusion coating usinghoppers such as described in U.S. Pat. No. 2,681,294 of Beguin issuedJune 15, 1954. If desired, two or more layers can be coatedsimultaneously such as by the procedures described in 'U.S. Pat. No.2,761,791 of Russell issued Sept. 4, 1956, and British Pat. No. 837,095.

If desired, thephotosensitive silver halide can be prepared in situ, inthe photosensitive and thermosensitive coatings of an element employedin the practice of the invention. Such a method is described, forexample, in U.S.Pat. No. 3,457,075 of Morgan et al. issued July 22,1969. For example, a dilute solution of a halogen acid such ashydrochloric acid can be applied to the surface of a thin coatingcontaining an organic silver salt, such as silver behenate, on asuitable substrate followed by removal of the solvent, if desired.Silver halide is thus formed in situ throughout the surface of thecoating of the organic silver salt.

The photosensitive silver halide can be prepared on the oxidizing agent,such as silver behenate or silver stearate or other organic silver salt,prior to application of the silver halide on the support employed. Thisis also described in U.S. Pat. No. 3,457,075 of Morgan et al. issuedJuly 22, 1969. For example, a halogen acid such as hydrochloric acid orhydrobromic acid can be mixed with an organic silver salt in a suitablereaction medium. A halide salt more soluble than the organic silver saltcan be added to a suspension of the organic silver salt to form thesilver halide. A suitable reaction medium includes water or othersolutions which do not interfere with the reaction.

Stability to print-out from light exposure is increased by employinghighly purified materials; for example, freedom from halides andsulfides increases stability to light exposure. The use of highlypurified silver behenate can, for example, reduce propensity to printoutin background areas of an element prepared according to the invention.

A range of azole thioethers and/or blocked azole thiones can be employedin the practice of the invention to improve post-processing stability,e.g., to reduce post-processing print-out due to room-light exposure andto reduce background stain. A suitable stabilizer precursor is aheterocyclic stabilizer precursor which is an azole compound of theformula:

wherein Z represents atoms completing a or 6- member heterocyclicnucleus, such as thiazole, thiadiazole, thiazoline and tetrazole; R isalkyl containing l to carbon atoms, e.g., methyl, ethyl, propyl, butyland pentyl,

or a heterocyclic group, e.g., furoyl; R is wherein R is alkylcontaining one to five carbon atoms, such as methyl, ethyl, propyl,butyl and pentyl, carboxy, cyano, aryl containing six to 12 carbonatoms, substituted aryl such as nitrophenyl, methoxyphenyl, ethoxyphenylor heterocyclic such as furoyl; R is hydrogen, alkyl containing one tofive carbon atoms, substituted alkyl such as oxoalkyl, carboxy andcarboxyalkyl; R is hydrogen, alkyl containing one to five carbon atomssuch as methyl, ethyl, propyl, butyl, tert.-.

butyl and pentyl, substituted alkyl such as hydroxymethyl, carboxy andcarboxyalkyl, aryl, substituted aryl, e.g., nitrophenyl, methoxyphenyl,benzoyl; n is 0 or 2. Alkyl as employed herein includes alkyl containingsubstituent groups which do not adversely affect the desired stabilizingactivity of the described compounds. The alkyl group can be, forexample, carboxyalkyl or dicarboxyalkyl.

An especially suitable thiazole thioether is S-acetyl-4-methyl-2-(3-oxobutylthio )thiazole ofthe formula:

wherein R is as described previously; R is alkyl containing one to fivecarbon atoms, aryl containing 6 to l2 carbon atoms, or furoyl; n is 0 or2.

An especially suitable thiadiazole thioether is 4-furoyl-3-methylthio-1,2,4-thiadiazole-5-thione of the formula:

Other examples of suitable thiadiazole thioether stabilizer precursorswhich can be employed in the practice of the invention include:

4-Furoyl-3-( 3-oxobutylthio)-1 ,2,4-thiadiazole-5- I thione,

3-Me'thylthio-4-benzoyl-l ,2,4-thiadiazole-5-thione,

4-Acetyl-3-methylthio-l ,2,4-thiadiazole-5 -thione or4-Acetyl-3-furoylethylthiol ,2,4-'thiadiazole-5- thione.

Still another suitable azole thioether stabilizer precursor which can beemployed in the desired combination includes, for example, tetrazolethioethers of the formula:

wherein R is phenyl, substituted phenyl such as 2,6-dit-butyl-phenyl,alkyl or wherein R is as described previously; R, can be alkyl,especially alkyl containing one to three carbon atoms, such as methyl,ethyl and propyl, and aryl, such as phenyl; n is or 2.

An especially suitable tetrazole thioether is 2,6- ditert.-butyl-4-(l-phenyl--tetrazolyl)thiophenyl of the formula: n V

wherein R R and R and n are as described previously. An especiallysuitable blocked azole thione is 5-acetyl-4-methyl-3-(3-oxobutyl)thiazoline-Z-thione of the formula: v

g 8 CH- j i 0 CH -N-(OH1)1tiL-CH;

Other examples of suitable blocked thiazoline thione stabilizerprecursors which can be employed in the practice of the inventioninclude:

5-Acetyl-3-benzoyl-4-methylthiazoline-2-thione,4-Benzoylmethyl-3-benzoylthiazoline-Z-thione,3-Furoyl-4-hydroxymethylthiazoline-Z-thione,3-Benzoyl'4-hydroxymethylthiazoline-2-thione,3-Benzoyl-44ert.-butylthiazoline-Z-thione and 5-Carboethoxy-4-methyl-3-( 3-oxobutyl )thiazoline- 2-thione.

The described stabilizer precursors are suitable in a range ofconcentration; however, they are especially suitable at a concentrationfrom about 0.002 to about 0.10 mole of stabilizer precursorper mole ofoxidizing agent, e.g., silver behenate, according to the invention, inan element as described. The desired concentration will'depend onseveral factors, such as the particular image-forming combination andother components of the element, desired image, processing temperatureand the like.

A simple test may be used to determine whether or not a compound ormaterial is functioning as an image stabilizer as described. If thecompound, after incorporation in the invention as described, preventsthe build-up of background density or minimum density above 0.l0 withoutundue stain, as in following Example 2, in comparison to a coating, asin following Example l, where the stabilizer precursor has been omitted,then the compound is considered to be a suitable stabilizer.

It is believed that the described azole thioether and blocked azolethiones are the precursors of the actual moiety, compound or materialwhich, upon combination with undeveloped silver ions or radicals,prevent print-out due to room-light exposure and alleviate backgroundstain. However, the exact mechanism of stabilization is not fullyunderstood.

The azole thioethers and blocked azole thiones can be prepared by theMichael addition of 0:,B-unsaturated ketones such as methyl vinyl ketoneto 4- thiazoline-Z-thione. By carefully controlling the reactionconditions, either azole thioethers or blocked azole thiones can beprepared almost exclusively of one another as described in J.Heterocyclic Chem., 6, 397-401 (1969) of Humphlett. The thermalreversibility of some of the azole thioethers formed via the Michaeladdition to 4-thiazoline-2-thiones is reported in Canadian J. Chem., 44,2315-2321 (1966) of Allen et al.

Spectral-sensitizing dyes can be used conveniently to confer additionalsensitivity to the light-sensitive silver halide employed in thepractice of the invention. For instance, additional spectralsensitization can be obtained by treating the silver halide withasolution of a sensitizing dye in an organic solvent, or the dye can beadded in the form of a dispersion as described in British Pat. No.1,154,781. For optimum results, the dye can beadded tothe emulsioneither as a final step or at some earlier stage.

Sensitizing dyes useful in sensitizing silver halide emulsions aredescribed, for example, in U.S. Pat. No.

2,526,632 of Brooker et al. issued Oct. 24, 1950; U.S. Pat. No.2,503,776 of Sprague issued Apr. 11, 1950; U.S. Pat. No. 2,493,748 ofBrooker et al. issued Jan. 10, 1950; and U.S. Pat. No. 3,384,486 ofTaber et al. issued May '21, 1968. Spectral sensitizers, which can beused, include the cyanines, merocyanines, complex (trinuclear ortetranuclear) cyanines, holopolar cyanines, styryls, hemicyanines suchas enamine, hemicyanines, oxonols and hemioxonols. Dyes of the cyanineclasses can contain such basic nuclei as the thiazolines, oxazolines,pyrrolines, pyridines, oxazoles, thiazoles, selenazoles and imidazoles.Such nuclei can contain alkyl, alkylene, hydroxyalkyl, sulfoalkyl,carboxyalkyl, aminoalkyl, and enamine groups that can be fused tocarbocyclic or heterocyclic-ring systems wither unsubstituted orsubstituted with halogen, phenyl, alkyl, haloalkyl, cyano or alkoxygroups. The dyes can be symmetrical or unsymmetrical and can containalkyl, phenyl, enamine or heterocyclic substituents on the methineor'polymethine chain.

The merocyanine dyes can contain the basic nuclei described, as well asacid nuclei such as thiohydantoins, rhodanines, oxazolidenediones,thiazolidenediones, barbituric acids, thiazolineones and malononitrile.These acid nuclei can be substituted with alkyl, alkylene, phenyl,carboxyalkyl, sulfoalkyl, hydroxyalkyl, alkoxyalkyl, alkylamine groupsor heterocyclic nuclei. Combinations of these dyes can be used, ifdesired. In addition, supersensitizing addenda which do not absorbvisible light may be included such as, for instance, ascorbic acidderivatives, azaindenes, cadmium salts and organic sulfonic acid asdescribed in U.S. Pat. No. 2,933,390 of McFall et al. issued Apr. 19,1960, and U.S. Pat. No. 2,937,089 of Jones et al. issued May 17, 1960.

The sensitizing dyes and other addenda used in the practice of theinvention can be added from water solutions or suitable organic solventsolutions can be used. The compounds can be added using variousprocedures including, for example, those described in U.S. Pat. No.2,912,343 of Collins et al. issued Nov. 10, 1959; U.S. Pat. No.3,342,605 of McCrossen et al. issued Sept. 19, 1967; U.S. Pat. No.2,996,287 of Audran issued Aug. 15, 1961; and U.S. Pat. No. 3,425,835ofJohnson et al. issued Feb. 4, 1969.

A range of concentration of dye can be employed in the practice of theinvention. The desired concentration will be influenced by the desiredspectral sensitivity, other components in the system, the desired image,processing conditions and the like. Typically, a concentration of thedescribed sensitizing dye is about 0.05 to about 1 milligram per squarefoot of the described photographic and thermosensitive element, usuallyabout 0.1 milligram per square foot of dye being employed.

One embodiment of the invention is a photosensitive and thermosensitiveelement comprising a support, an oxidation-reduction image-formingcombination comprising (i) a heavy metal salt oxidizing agent, such as asilver salt oxidizing agent, with (ii) a reducing agent, such as abis-naphthol reducing agent, a catalyst for the describedoxidation-reduction image-forming combination, e.g., photosensitivesilver halide, a binder and a divalent metal salt image amplifier, e.g.,zinc acetate, copper acetate or cadmium acetate. For example, thephotosensitive element as described can comprise:

a. a support,

b. 2,2'-dihydroxyl ,1 '-binaphthyl reducing agent,

c. silver behenate oxidizing agent,

d. photosensitive silver halide,

e. polyvinyl butyral binder,

f. phthalimide activator-toning agent,

g. 5-acetyl-4-methyl-2-(3-oxobutylthio)thiazole image-stabilizerprecursor,

h. a sensitizing dye and i. a divalent metal salt image amplifier, suchas zinc acetate or cadmium acetate.

Another embodiment of the invention is a photosensitive andthermosensitive composition comprising:

a. an oxidation-reduction image-forming combination comprising (i) aheavy metal salt oxidizing agent, e.g., a silver salt oxidizing agent,with (ii) a reducing agent, e.g., a bis-naphthol reducing agent,

b. a catalyst for the described oxidation-reduction image-formingcombination, e.g., photosensitive silver halide, and

c. a divalent metal salt image amplifier which is a zinc, cadmium orcopper salt, as described. For example, the photosensitive andthermosensitive composition can comprise:

a. about 0.10 mole to about 2.0 moles, e.g., about 0.40 mole to about0.75 mole, of reducing agent, such as 2,2-dihydroxy-l,l'-binaphthyl, permole of heavy metal salt oxidizing agent, such as silver behenateoxidizing agent,

b. about 0.005 mole to about 0.50 mole of photosensitive silver salt permole of silver behenate oxidizing agent, and

c. about 0.005 mole to about 0.20 mole, e.g., about 0.010 mole to about0.10 mole, ofa zinc, cadmium or copper salt image amplifier per mole ofsilver behenate oxidizing agent.

After exposure of the described photosensitive and thermosensitiveelement, the resulting latent image is developed merely by heating theelement. A visible image on the photosensitive and thermosensitiveelement can'be produced within a few seconds, e.g., about 0.5 to about60 seconds, after exposure by heating the element to moderately elevatedtemperatures, e.g., about to about 250 C.

Accordingly, another embodiment of the invention IS: in a method ofdeveloping a latent image in an exposed photosensitive andthermosensitive element comprising a support, an oxidation-reductionimage-forming combination comprising (i) a heavy metal salt oxidizingagent with (ii) a reducing agent, a catalyst for the describedoxidation-reduction image-forming combination, a binder and a divalentmetal salt image amplifier which is a zinc, copper or cadmium salt,comprising heating said element to about 80 C. to about 250 C.

A temperature range of about C. to about C is usually suitable fordeveloping and stabilizing a desired image. By increasing or decreasingthe length of time of heating, a higher or lower temperature within thedescribed range can be employed. A developed image is typically producedwithin a few seconds, such as about 0.5 second to about 60 seconds.

The photographic process can comprise, for example, exposing to actinicradiation a photosensitive and thermosensitive element comprising asupport,

a. an oxidation-reduction image-forming combination comprising: Y

i. silver behenate oxidizing agent and ii. 2,2'-dihydroxy-l ,l-binaphthyl reducing agent,

b. photosensitive silver halide,

c. a divalent metal salt such as zinc acetate,

(1. polyvinyl butyral binder,

e. phthalimide activator-toning agent,

f. an image-stabilizer precursor such as 5-acetyl-4-methyl-2-(3-oxobutylthio)thiazole and g. a sensitizing dye, and heatingthe described element from about 80 C. to about 250 C. for about 0.5 toabout 60 seconds.

Processing is usually carried out under ambient conditions oftemperature, pressure and humidity. Temperatures, pressures and humidityoutside normal atmospheric conditions can be employed if desired;however, normal atmospheric conditions are preferred.

in some cases, if desired, an element can be prepared wherein thedescribed silver halide can be in one layer and other components inother layers. For example, an element according to the invention cancomprise a support, a layer containing photographic silver halide and alayer comprising a so-called thermosensitive processing compositioncomprising:

a. a heavy metal salt oxidizing agent, e.g., a silver salt oxidizingagent such as a silver salt of an organic acid,

b. a reducing agent, as described, such as a bisnaphthol reducing agent,

c. an activator-toning agent, as described, and

d. a divalent metal salt image amplifier, as described. An example ofsuch a processing composition is a thermosensitive processingcomposition comprising:

a. silver behenate,

b. 2,2'-dihydroxy-l ,l -binaphthyl,

c. phthalimide and d. zinc acetate. Typically, a polyvinyl butyralbinder is employed with the processing composition.

As another example, it is sometimes advantageous to incorporate thebis-B-naphtho] reducing agent and/or the zinc acetate in a polyvinylbutyral or cellulose acetate binder and to coat the resultingcomposition as an anti-abrasion overcoat on the element as describedpreviously.

Various methods can be employed in providing the necessary heating ofthe described photosensitive and thermosensitive elements. The heatingmeans can be a simple hot plate, iron or the like.

Other addenda are known to be useful in photosensitive andthermosensitive elements of this type, such as described in BritishPatent No. 1,161,777 published Aug. 20, 1969, U.S. Pat. No. 3,152,904 ofSorensen and Shepard issued Oct. 13, 1964, and U.S. Pat. No. 3,457,075of Morgan and Shely issued July 22, 1969.

The following examples are included for a further.

understanding of the invention.

EXAMPLE 1 This is a comparative example.

A photosensitive element is prepared as follows:

A coating composition is prepared by mixing the following components:

Silver behenate 42.00 g. Behenic acid 32.00 g. Polyvinyl butyral 15.00g. Sodium bromide (reacts with silver 0.25 g. behenate to form silverbromide in situ) Phthalimide 8.50 g. Acetone-toluene (1:1 by volume) 500ml.

After ball-milling for about 24 hours, 72.0 milliliters of the abovedispersion is combined with the following solutions:

Acetone containing 1.0 mg./ml. of 3- 0.3 ml.

background stain.

EXAMPLE 2 This illustrates the invention.

The procedure set out in Example 1 is repeated with the exception that2.5 ml. of a methanol solution containing 1.0 percent by weight of zincacetate is added to the final dispersion just prior to making thecoating.

The final element is exposed and processed as in Example 1; theresulting image is jet-black, has a maximum density of 1.24 and aminimum density of 0.04. A 21.5

percent increase in image density is realized in comparison to Example1.

EXAMPLE 3 This illustrates the invention.

Similar results are obtained as in Example 2 upon substitution ofcadmium acetate for zinc acetate.

EXAMPLE 4 This illustrates the invention.

Similar results are obtained as in Example 2 upon substitution of cupricacetate for zinc acetate.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be effected within the spirit and scopeof the invention.

1 claim:

1. In a photosensitive and thermosensitive element comprising a supporthaving thereon an oxidationreduction image-forming combinationcomprising (i) a heavy metal salt oxidizing agent with (ii) a reducingagent, a photosensitive silver salt catalyst for saidoxidation-reduction image-forming combination and a binder; theimprovement comprising a divalent metal salt image amplifier which is azinc, copper or cadmium salt.

2. A photosensitive and thermosensitive element comprising a supporthaving thereon a. an oxidation-reduction image-forming combinationcomprising (i) a silver salt oxidizing agent and (ii) a bis-beta-naptholreducing agent,

b. a catalyst for said oxidation-reduction imageforming combinationcomprising photosensitive silver halide,

c. a divalent metal salt image amplifier which comprises zinc acetateand d. a binder.

3. A photosensitive and thermosensitive element as in claim 2 alsocomprising an activator-toning agent.

4. A photosensitive and thermosensitive element as in claim 2 alsocomprising an activator-toning agent which is phthalimide.

5. A photosensitive and thermosensitive element as in claim 2 alsocomprising a stabilizer precursor which is an azole thioether or ablocked azole thione.

6. A photosensitive and thermosensitive element as in claim 2 alsocomprising a stabilizer precursor which is 5 -acetyl-4-methyl-2-(3-oxobuty1thio )thiazole.

7. A photosensitive and thermosensitive element comprising a supporthaving thereon a. an oxidation-reduction image-forming combinationcomprising (i) an oxidizing agent comprising silver behenate and (ii) areducing agent which is 2,2'-dihydroxy-1,1'-binaphthyl,

b. photosensitive silver halide,

c. a divalent metal salt image amplifier which is zinc acetate,

d. polyvinyl butyral binder,

e. phthalimide activator-toning agent, and

f. a sensitizing dye.

8. A photosensitive and thermosensitive element as in claim 2 alsocomprising a sensitizing dye.

9. A photosensitive and thermosensitive element as in claim 2 comprisinga support having thereon a. about 0.10 mole to about 2.0 moles of saidreducing agent per mole of said catalyst,

b. about 0.005 mole to about 0.50 mole of said catalyst per mole of saidoxidizing agent and c. about 0.005 mole to about 0.20 mole of said zincacetate per mole of said oxidizing agent.

10. A photosensitive and thermosensitive composition comprising:

a. an oxidation-reduction image-forming combination comprising (i) aheavy metal salt oxidizing agent with (ii) a reducing agent,

b. a photosensitive silver salt catalyst for said oxidation-reductionimage-forming combination and c. a divalent metal salt image amplifierwhich is a zinc, copper or cadmium salt.

11. A photosensitive and thermosensitive composition comprising:

a. an oxidation-reduction image-forming combination comprising (i) asilver salt oxidizing agent with (ii) a bis-beta-naphthol reducingagent,

b. a catalyst for said oxidation-reduction imageforming combinationcomprising photosensitive silver halide and c. a divalent metal saltimage amplifier which com-' prises zinc acetate.

12. A photosensitive and thermosensitive composition as in claim 11 alsocomprising an activator-toning agent.

13. A photosensitive and thermosensitive composition as in claim 11 alsocomprising an activator-toning agent which is phthalimide.

14. A photosensitive and thermosensitive composition as in claim 11 alsocomprising a stabilizer precursor which is an azole thioether or ablocked azole thione.

15. A photosensitive and thermosensitive composition comprising:

a. an oxidation-reduction image-forming combination comprising (i) anoxidizing agent comprising silver behenate and (ii) a reducing agentwhich is 2,2'-dihydroxy-l,l'-binaphthyl,

b. photosensitive silver halide,

c. a divalent metal salt image amplifier which is zinc acetate,

d. polyvinyl butyral binder,

e. phthalimide activator-toning agent,

f. an image-stabilizer precursor comprising S-acetyl-4-methyl-2--(3-oxobutylthio)thiazole and g. a sensitizing dye.

16. A photosensitive and thermosensitive composition as in claim 11 alsocomprising a sensitizing dye.

17. A photosensitive and thermosensitive composition as in claim 11comprising:

a. about 0.10 mole to about 2.0 moles of said reducing agent per mole ofsaid oxidizing agent,

b. about 0.005 to about 0.50 mole of said catalyst per mole of saidoxidizing agent and c. about 0.005 mole to about 0.20 mole of said zinc,copper or cadmium salt per mole of said oxidizing agent.

18. A method of developing an image in an exposed photosensitive andthermosensitive element comprising a support having thereon anoxidation-reduction image-forming combination comprising (i) a heavymetal salt oxidizing agent with (ii) a reducing agent, a

photosensitive silver salt catalyst for said oxidationreductionimage-forming combination, a binder and a divalent metal salt imageamplifier which is a zinc, copper or cadmium salt, comprising heatingsaid element to about C to about 250 C. i

19. A method of developing and stabilizing an image in an exposedphotosensitive and thermosensitive element comprising a support,

a. an oxidation-reduction image-forming combination comprising (i) asilver salt oxidizing agent and (ii) a bis-beta-naphthol reducing agent,

b. a catalyst for said oxidation-reduction imageforming combinationcomprising photosensitive silver halide,

c. a divalent metal salt image amplifier which comprises zinc acetate, abinder, e. an activator-toning agent and f. an image-stabilizerprecursor which is an azole thioether or a blocked azole thione,comprising heating said element to about 80 C. to about 250 C. e 20. Amethod of developing and stabilizing an image in an exposedphotosensitive and thermosensitive element comprises a support, havingthereon a. an oxidation-reduction image-forming combination comprising(i) an oxidizing agent comprising silver behenate and (ii) a reducingagent comprising 2,2'-dihydroxy-l ,l '-binaphthyl,

b. photosensitive silver halide,

c. a divalent metal salt image amplifier which is zinc acetate,

d. polyvinyl butyral binder,

e. phthalimide activator-toning agent,

f. an image-stabilizer precursor comprising S-acetyl-4-methyl-2-(3-oxobutylthio)thiazole and g. a sensitizing dye, comprisingheating said element to about 80 C. to about 250 C.

21. A method as in claim 20 comprising heating said element for about0.5 to about 60 seconds.

22. A thermosensitive processing composition comprising:

a. a silver salt oxidizing agent,

b. a bis-beta-naphthol reducing agent,

c. an activator-toning agent and d. a divalent metal salt imageamplifier.

23. A thermosensitive processing composition comprising:

a. silver behenate,

b. 2,2'-dihydroxy-l,l '-binaphthyl,

c. phthalimide and d. zinc acetate.

24. A thermosensitive processing composition as in claim 22 comprisingpolyvinyl butyral binder.

25. The photosensitive and thermosensitive element of claim 1 whereinsaid divalent metal salt image amplifier is present in a concentrationof about 0.005 mole to about 0.20 mole of said divalent metal salt imageamplifier per mole of said oxidizing agent.

26. The photosensitive and thermosensitive composition of claim 10wherein said divalent metal salt image amplifier is present in aconcentration of about 0.005 mole to about 0.20 mole of said divalentmetal salt image amplifier per mole of said oxidizing agent.

2. A photosensitive and thermosensitive element comprising a supporthaving thereon a. an oxidation-reduction image-forming combinationcomprising (i) a silver salt oxidizing agent and (ii) a bis-beta-naptholreducing agent, b. a catalyst for said oxidation-reduction image-formingcombination comprising photosensitive silver halide, c. a divalent metalsalt image amplifier which comprises zinc acetate and d. a binder.
 3. Aphotosensitive and thermosensitive element as in claim 2 also comprisingan activator-toning agent.
 4. A photosensitive and thermosensitiveelement as in claim 2 also comprising an activator-toning agent which isphthalimide.
 5. A photosensitive and thermosensitive element as in claim2 also comprising a stabilizer precursor which is an azole thioether ora blocked azole thione.
 6. A photosensitive and thermosensitive elementas in claim 2 also comprising a stabilizer precursor which is5-acetyl-4-methyl-2-(3-oxobutylthio)thiazole.
 7. A photosensitive andthermosensitive element comprising a support having thereon a. anoxidation-reduction image-forming combination comprising (i) anoxidizing agent comprising silver behenate and (ii) a reducing agentwhich is 2,2''-dihydroxy-1,1''-binaphthyl, b. photosensitive silverhalide, c. a divalent metal salt image amplifier which is zinc acetate,d. polyvinyl butyral binder, e. phthalimide activator-toning agent, andf. a sensitizing dye.
 8. A photosensitive and thermosensitive element asin claim 2 also comprising a sensitizing dye.
 9. A photosensitive andthermosensitive element as in claim 2 comprising a support havingthereon a. about 0.10 mole to about 2.0 moles of said reducing agent permole of said catalyst, b. about 0.005 mole to about 0.50 mole of saidcatalyst per mole of said oxidizing agent and c. about 0.005 mole toabout 0.20 mole of said zinc acetate per mole of said oxidizing agent.10. A photosensitive and thermosensitive composition comprising: a. anoxidation-reduction image-forming combination comprising (i) a heavymetal salt oxidizing agent with (ii) a reducing agent, b. aphotosensitive silver salt catalyst for said oxidation-reductionimage-forming combination and c. a divalent metal salt image amplifierwhich is a zinc, copper or cadmium salt.
 11. A photosensitive andthermosensitive composition comprising: a. an oxidation-reductionimage-forming combination comprising (i) a silver salt oxidizing agentwith (ii) a bis-beta-naphthol reducing agent, b. a catalyst for saidoxidation-reduction image-forming combination comprising photosensitivesilver halide and c. a divalent metal salt image amplifier whichcomprises zinc acetate.
 12. A photosensitive and thermosensitivecomposition as in claim 11 also comprising an activator-toning agent.13. A photosensitive and thermosensitive composition as in claim 11 alsocomprising an activator-toning agent which is phthalimide.
 14. Aphotosensitive and thermosensitive composition as in claim 11 alsocomprising a stabilizer precursor which is an azole thioether or ablocked azole thione.
 15. A photosensitive and thermosensitivecomposition comprising: a. an oxidation-reduction image-formingcombination comprising (i) an oxidizing agent comprising silver behenateand (ii) a reducing agent which is 2,2''-dihydroxy-1,1''-binaphthyl, b.photosensitive silver halide, c. a divalent metal salt image amplifierwhich is zinc acetate, d. polyvinyl butyral binder, e. phthalimideactivator-toning agent, f. an image-stabilizer precursor comprising5-acetyl-4-methyl-2-(3-oxobutylthio)thiazole and g. a sensitizing dye.16. A photosensitive and thermosensitive composition as in claim 11 alsocomprising a sensitizing dye.
 17. A photosensitive and thermosensitivecomposition as in claim 11 comprising: a. about 0.10 mole to about 2.0moles of said reducing agent per mole of said oxidizing agent, b. about0.005 to about 0.50 mole of said catalyst per mole of said oxidizingagent and c. about 0.005 mole to about 0.20 mole of said zinc, copper orcadmium salt per mole of said oxidizing agent.
 18. A method ofdeveloping an image in an exposed photosensitive and thermosensitiveelement comprising a support having thereon an oxidation-reductionimage-forming combination comprising (i) a heavy metal salt oxidizingagent with (ii) a reducing agent, a photosensitive silver salt catalystfor said oxidation-reduction image-forming combination, a binder and adivalent metal salt image amplifier which is a zinc, copper or cadmiumsalt, comprising heating said element to about 80* C to about 250* C.19. A method of developing and stabilizing an image in an exposedphotosensitive and thermosensitive element comprising a support, a. anoxidation-reduction image-forming combination comprising (i) a silversalt oxidizing agent and (ii) a bis-beta-naphthol reducing agent, b. acatalyst for said oxidation-reduction image-forming combinationcomprising photosensitive silver halide, c. a divalent metal salt imageamplifier which comprises zinc acetate, d. a binder, e. anactivator-toning agent and f. an image-stabilizer precursor which is anazole thioether or a blocked azole thione, comprising heating saidelement to about 80* C. to about 250* C.
 20. A method of developing andstabilizing an image in an exposed photosensitive and thermosensitiveelement comprises a support, having thereon a. an oxidation-reductionimage-forming combination comprising (i) an oxidizing agent comprisingsilver behenate and (ii) a reduciNg agent comprising2,2''-dihydroxy-1,1''-binaphthyl, b. photosensitive silver halide, c. adivalent metal salt image amplifier which is zinc acetate, d. polyvinylbutyral binder, e. phthalimide activator-toning agent, f. animage-stabilizer precursor comprising5-acetyl-4-methyl-2-(3-oxobutylthio)thiazole and g. a sensitizing dye,comprising heating said element to about 80* C. to about 250* C.
 21. Amethod as in claim 20 comprising heating said element for about 0.5 toabout 60 seconds.
 22. A thermosensitive processing compositioncomprising: a. a silver salt oxidizing agent, b. a bis-beta-naphtholreducing agent, c. an activator-toning agent and d. a divalent metalsalt image amplifier.
 23. A thermosensitive processing compositioncomprising: a. silver behenate, b. 2,2''-dihydroxy-1,1''-binaphthyl, c.phthalimide and d. zinc acetate.
 24. A thermosensitive processingcomposition as in claim 22 comprising polyvinyl butyral binder.
 25. Thephotosensitive and thermosensitive element of claim 1 wherein saiddivalent metal salt image amplifier is present in a concentration ofabout 0.005 mole to about 0.20 mole of said divalent metal salt imageamplifier per mole of said oxidizing agent.
 26. The photosensitive andthermosensitive composition of claim 10 wherein said divalent metal saltimage amplifier is present in a concentration of about 0.005 mole toabout 0.20 mole of said divalent metal salt image amplifier per mole ofsaid oxidizing agent.
 27. The method of claim 18 wherein said divalentmetal salt image amplifier is present in a concentration of about 0.005mole to about 0.20 mole of said divalent metal salt image amplifier permole of said oxidizing agent.